How Long Does Metronidazole Stay In The Body?
In our latest question and answer, the pharmacist discusses how long Flagyl (metronidazole) lasts in the body.
How long does it take for the total removal of metronidazole and its metabolites from the body? I have taken metronidazole for 7 days for Trichomonas intestinalis. This is the second day after ending the full dose I have been administered. But until now, I have had side effects, like nausea, vomiting, headache, and decreased libido... I'm wondering when its effects will stop.
Sep 22, 2022- Metronidazole is completely eliminated from your body in about 2 to 3 days after your last dose.
- You should avoid alcohol during treatment and for up to 3 days after your last metronidazole dose because it can cause serious side effects like nausea, vomiting, and increased heart rate.
- Side effects from metronidazole typically resolve within a few hours of dosing or within a few days after stopping the medication.
Answer
Thanks for your question!
Metronidazole is metabolized and eliminated from the body completely around 2 to 3 days after your last dose. I describe this in more detail in the sections below.
What Is Metronidazole?
Metronidazole (brand name Flagyl) is an antibiotic and antiprotozoal agent that is used for a variety of indications including pneumonia, respiratory infections, intra-abdominal infections, and bacterial vaginosis.
Once taken by mouth, metronidazole is quickly absorbed and reaches peak concentration in the blood after one to three hours. When taken with food, the rate of absorption decreases but not the overall extent of absorption. The overall effect of metronidazole when taken with food, however, is unchanged.
Metronidazole Metabolism
Metronidazole is mostly metabolized in the liver and is excreted via the urine and feces.
Per the prescribing information, the half-life (time for 50% of the drug to be metabolized) is about 8 hours. A general rule of thumb is that it takes about 5 half-lives for a drug to be considered completely metabolized. Therefore, it should take about 2 to 3 days for metronidazole to be completely eliminated from the body.
If metronidazole is causing side effects, such as nausea, diarrhea, or vomiting, you can expect them to resolve a few hours after dosing, or at the very latest, within a few days after the last dose was taken.
Avoid Alcohol With Metronidazole
One of the major precautions with metronidazole is the need to avoid alcohol consumption while taking the drug. Metronidazole can alter the metabolism of alcohol and increase the amount of a toxic metabolite, acetaldehyde. The use of alcohol and metronidazole together can cause a "Disulfiram-like" reaction. Potential side effects include:
- Nausea
- Vomiting
- Increased heart rate
- Headache
- Flushing
- Abdominal cramps
Generally, it is recommended to avoid alcohol and alcohol-containing products (e.g cough medications with alcohol) during and for up to 3 days after the last dose of metronidazole.
Final Words
Thanks again for your question and reach back out anytime!
References & sources
Glossary — Terms in This Answer
- Antibiotic
- A medication that kills or stops the growth of bacteria.
- Antiprotozoal agent
- A medication that kills or stops the growth of protozoa, which are single-celled parasitic organisms.
- Absorbed
- Taken in and passed through the digestive system into the bloodstream.
- Peak concentration
- The highest level of a drug present in the blood after taking a dose.
- Metabolized
- Broken down by the body, usually in the liver, into forms that can be used or eliminated.
- Excreted
- Eliminated from the body through waste products like urine or feces.
- Half-life
- The amount of time it takes for half of a drug dose to be metabolized and removed from the body.
- Disulfiram-like reaction
- A severe adverse reaction caused by mixing alcohol with certain medications, causing symptoms like nausea, vomiting, and flushing.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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